Tracking specific start variance

Situation: Project Plan is baselined. Activity A is predecessor to Activity B and was completed a week behind schedule. Activity B started 3 days after Activity A was completed. Is there a way to measure the start variance due to delay in Activity B alone (i.e. 3 days). (Right now the Start Variance of Activity B is inclusive of the delay in Activity A i.e. 5 days + 3 days).

Joseph, I don't know of a completely automatic way but there may be combination of process and macro that would help.
Suppose your process is that:
You update all task completions first - get those actual finish dates on your Task As.
Then run a macro to snap early finish date for any unstarted tasks into a custom date field.
Then accept task updates for tasks starting (your Task Bs)
Now the difference between your captured early start date in the custom field and the Actual start date will be the start delay that is not due to Task A.

The process and macro would need a bit of tweaking - and there are probably some wrinkles that would be caused by other task changes not related to actual starts and finishes but I think the logic is generally sound.